Analyte concentration determination in physiological samples is of ever increasing importance to today's society. Such assays find use in a variety of application settings, including clinical laboratory testing, home testing, etc., where the results of such testing play a prominent role in the diagnosis and management of a variety of disease conditions. Analytes of interest include glucose for diabetes management, cholesterol for monitoring cardiovascular conditions, and the like. In response to this growing importance of analyte concentration determination, a variety of analyte concentration determination protocols and devices for both clinical and home testing have been developed.
Before testing can begin, an individual seeking to determine the presence and/or concentration of an analyte in a physiological sample must first obtain a test strip, apply a sample thereto and obtain the results, either manually or automatically with a meter or the like. However, obtaining a test strip to begin the procedure is not without difficulty. For example, diabetics typically have visual and/or dexterity problems, thus making the selection of a single test strip, which usually has a length of about 50 mm and a width of about 7 mm, from a plurality of such test strips difficult.
Typically, a plurality of test strips are stored in a relatively large vessel, i.e., a vessel large enough to hold a plurality of test strips and to completely encompass the test strips inside so as to protect the test strips from light, humidity, and other environmental contaminants including oils and the like from a user's hands, where such protection is necessary to insure the precision, accuracy and overall integrity of the test result. An exemplary embodiment of a subject test strip storage vessel is shown in FIG. 1. Thus, to obtain a single test strip from the vessel to begin a test, an individual has two options for removing a test strip. In one option, an individual may simply turn the vessel upside down to pour a test strip out. This, as is apparent, has significant disadvantages as the test strips stored inside the vessel may quickly spill onto out and becomes contaminated. In a second option, an individual places a finger inside the vessel to try to grasp a single test strip amongst a plurality of test strips without damaging any of the strips in the process. However, such a method oftentimes results in the user inadvertently contacting portions of the test strip that should not be touched, such as testing or reaction areas (i.e., areas on the strip having testing reagents, etc.) and the like, where such contact can impart contaminants and cause erroneous testing results. Similarly, other test strips may be inadvertently contacted resulting in erroneous testing results of those test strips as well.
Furthermore, the vessel must have a suitable shape and sized large enough to accommodate at least one finger therein, for easy removal of a test strip. In other words, the vessel must enable an individual, i.e., an individual who may be visually and dextrally impaired, to retrieve a test strip from amongst a plurality of test strips without damaging or contaminating any of such test strips.
However, it can be appreciated that the vessel, while maintaining a size large enough to serve its functions, must be small enough to enable portability of the vessel so that an individual may easily carry the vessel at all times to accommodate testing during the course of a day. However, due to the above described shape and size requirements, conventional vessels typically have a circular cross-sectional shape to accommodate insertion of at least one finger therein, have a height of about 60 mm and a diameter of about 25 mm and are commercially sold with about 25 test strips retained therein. As is apparent, such size and shape creates a great amount of unused space inside the vessel and minimizes the portability of the vessel. In other words, the vessels are larger than necessary to simply hold the test strips, thus increasing costs and decreasing portability.
U.S. Pat. No. 4,911,344 to Kahler discloses a strip dispenser box capable of dispensing a single test strip from a stack of test strips that does not require the user to insert a finger inside a vessel to retrieve a test strip. Rather, the '344 patent discloses a cap assembly with a strip feeder mechanism mounted to a housing having a magazine capable of holding a stack of test strips. The cap has a slot therein and a slide bar assembly slideably mounted in the slot for moving a test strip out of the dispenser, more particularly out of a gasket-sealed opening positioned on the cap assembly. However, the device disclosed in the '344 patent suffers from certain disadvantages. First and foremost, the strip dispenser of the '344 patent fails to maintain a completely moisture free environment. Specifically, at least two areas of the dispenser permit moisture to enter the housing and thus contact the test strips therein.
The first area which fails to provide a moisture free seal is the slot/slide bar assembly area. The slide bar is made of a cross shaped base member slideably positioned on the inner surface of the cap body and a finger grip which extends upward through the slot of the cap assembly. In operation, the finger grip is driven forward by the action of the thumb of the user and it carries a test strip out an opening of the cap assembly. As described in the patent, the preferred material of the dispenser is polyethylene plastic. In other words, both the cap assembly (the slot area) and the slide bar are made of polyethylene plastic. It will be apparent to one of skill in the art that such an assembly of two contacting polyethylene plastic surfaces cannot provide an adequate barrier to moisture.
The second area which fails to provide a moisture free seal is the opening through which a test strip is removed from the dispenser, even though a seal strip or gasket extends about {fraction (1/32)} of an inch into the dispenser and covers the opening thereto. In other words, a gasket or the like is attached on a first side to the cap assembly and unattached on its other sides to allow a test strip to be pushed therethrough. It will similarly be apparent to one of skill in the art that such a seal cannot provide a barrier to moisture.
As will be apparent to those of skill in the art, the efficiency of a seal between two surfaces touching each other depends on the surface materials and the pressure exerted by one surface to the other or, in other words, the normal or perpendicular forces holding the surfaces together.
With respect to the first area which fails to provide a moisture free seal, the seal between the slide bar surface and the mating surface of the opening through which it extends is not efficient because attempts to form a perfect seal or increase the sealing ability by making the surfaces flatter or more resilient will increase the coefficient of friction between the two surfaces, making it more difficult to slide or move the bar in relation to the body of the device, as needed to dispense a test strip. Increasing the normal force between the two surfaces to form a perfect seal or increase the sealing ability will also increase the force needed to slide the bar.
With respect to the second area which fails to provide a moisture free seal, any attempt to increase the load to hold the two surfaces together in order to increase the seal efficiency would require an increase in the load on the end of the test strip being dispensed to push the gasket out of the way as the strip exits. This load could buckle or damage the test strip and would also increase the load on the slide bar by the user.
As such, there is continued interest in the development of new devices and methods for use in test strip dispensing. Of particular interest would be the development of such devices and methods which are easy and inexpensive to manufacture, easy to use, particularly for visually and dextrally impaired individuals, are portable and which prevent damage to the test strips from light, humidity, and other environmental contaminants including oils and the like from a user's hands.